The invention relates to a tool holder for shrink-fit attachment of rotating tools with predominantly cylindrical shafts.
In a known tool holder of this kind (U.S. Pat. No. 6,315,506 B1), the chuck is provided with a socket in the center for an insert; this central socket of the chuck has a cylindrical inner bore that widens out in an approximately conical fashion toward its open end. This socket can accommodate the entire length of an insert, which is correspondingly adapted to have one longitudinal segment with a cylindrical outer surface and an adjoining longitudinal segment with a conical outer surface, the two longitudinal segments being accommodated in a precisely fitting way inside the socket of the chuck. In the region of the cylindrical longitudinal segment, the insert has a threaded bore that is engaged by a coaxial threaded screw whose screw head is supported axially against the chuck. The insert is detachably fixed in the socket of the chuck by tightening this central screw; spaced axially apart from the threaded section that accommodates the screw, a cylindrical inner bore is provided to accommodate the tool shaft. The tool shaft is clamped radially by shrink-fitting action by means of the conical receiving bore in the clamping section of the chuck and the conical outer surface of the insert. In order to assure a secure clamping of cylindrical tool shafts in these chucks, the tool shafts must be manufactured very precisely, with small diameter tolerances, and must be matched to the bore of the insert. Furthermore, only relatively weak radial clamping forces can be produced. Tool shafts with large diameter tolerances, e.g. of the kind that occur in tools used for woodworking, cannot be clamped with a tool holder of this kind or can only be clamped in an unreliable way.
The object of the invention is to provide a tool holder of the type mentioned at the beginning, which permits a secure clamping, even of tool shafts with large diameter tolerances.